Field of the Invention
The present invention relates to prospecting devices, and more particularly to a foot operated shaker assembly useful to shake and agitate screen bottomed classifying pans in coordination with the manual shoveling strokes to sift and separate, or classify, the ore bearing soil from any admixed rock aggregate shoveled into the pan.
Description of the Prior Art
Precious metals like gold and silver are characterized by their very high specific gravity, fairly low melting temperatures and also a very malleable or ductile material structure that is easily fragmented both by the high temperatures of the tectonic processes and also by the subsequent weathering when these processes cool down. As result the recovery of these highly macerated and finely distributed metals is invariably associated with moving enormous quantities of ore-bearing soil and rock which then needs to be sorted, classified and thereafter processed to a point where the sought metal is finally isolated and then collected. Of course, the back-breaking movement of these huge volumes of the earth's mantle produced all sorts of mechanical, chemical and hydraulic aids which, by their cost, complexity and toxic consequence are mainly useful in larger ground formations rich in the metal deposits, leaving the small, highly localized by alluvial processes, placer deposits to the individual prospector.
Of course, the same high specific gravity and easily fractioned, low strength material structure of the mined precious metal resulted in similar, or even greater, need for mechanical assistance at these smaller placer mining sites and to assist this individual prospector, way out in the desolate terrain where these alluvial concentration sites are often found, various more compact, trailer borne sorting and sifting assemblies were devised as exemplified in the teachings of U.S. Pat. No. 5,421,461 to Razic; U.S. Pat. No. 5,842,578 to Cordeiro; and many others. While suitable for the purposes intended, each of the foregoing examples either entail a substantial storage burden when not in use, and therefore are beyond the capacity of the occasional prospector, or require an elaborate and time consuming assembly at the placer site that often is not justified by its potential.
Significantly, the material structure and density of the mined metal referred to above also focuses the primary processing efforts to those associated with classifying by particle size large volumes of the alluvial concentrate within the placer deposits. As result a variety of smaller, highly compact and easily loaded onto the bed of a pickup truck, screening and classifying mechanisms have been devised exemplified in the teachings of U.S. Pat. No. 5,423,430 to Zaffiro et al.; U.S. Pat. No. 7,591,377 to Puda et al.; U.S. Pat. No. 8,113,355 to Peterson; and many others.
While again suitable for the purposes intended, each of the foregoing entails an interruption of the manual shoveling of the placer's deposits onto one or more of the classifying screens so that the screen or screens may be then agitated or shaken to help pass the properly sized particulates therethrough for collection in buckets or trays, with the shoveling then resumed once more until the screen or screens are fully covered with the accumulated larger particulate loads. Once thus fully loaded the screens need to be lifted and emptied to allow the process to continue. These interruptions prolong to agonizing lengths the already tedious, back-breaking process and a mechanism that utilizes the movement associated with a shoveling stroke to also agitate the screen that is then easily relieved of its accumulated load directly from the shoveling stance is therefore extensively desired and it one such mechanism that is described herein.